JP6589106B2 - Modulated wave resolver device - Google Patents

Description

The present invention relates to a modulated wave resolver device that has a function of generating respective modulated waves from orthogonal two-phase PWM signals of SIN and COS and detects a phase angle corresponding to a rotation angle.

The goal of the Japanese government is to create a 30 trillion yen market in 2020 by the “Fourth Industrial Revolution” in April 2016, which will significantly increase productivity by utilizing artificial intelligence (AI) and robot technology. 10 priority projects have been launched.
Because of these demands, AI-based robot development plans are in progress as a national strategy.
AI-equipped robots are multi-axis and multi-joint, and are equipped with a number of rotation sensors in combination with servo motors. They are also promising as sensors connected to the IoT.
Compared with the winding type, the modulation wave resolver has a higher excitation sensitivity, and the detection sensitivity is increased, the number of coil turns is greatly reduced, and the coil can be printed. As a result, the structure is simple, lightweight and compact. It has excellent characteristics as a rotation sensor.

Patent No. 3047231

As shown in Japanese Patent No. 3047231, although the mechanical configuration of the modulated wave resolver is simple and has excellent characteristics, at present, the electronic control circuit that drives this modulated wave is complicated and expensive, This is a major obstacle to the spread of the modulated wave resolver itself.
The current high frequency (about 500kHz) modulation wave generation is realized by FPGA, two D / A converters and drivers, but since the modulation wave is high frequency, two D / A converters are required. There is a problem that it is expensive and the circuit mounting area is large.

The present invention realizes modulation wave generation by a PWM method with a simple structure and a small number of parts.
The PWM method realizes modulation wave generation with two PWM serial lines of SIN and COS, a power switch and a bandpass filter. The circuit is downsized by greatly reducing the number of parts, parts cost, and mounting space.

  By applying the PWM method to the modulated wave resolver device of the present invention, the modulated wave resolver device can be reduced in size, weight, improved environmental resistance, extended life, and reduced cost. Due to the effect of such miniaturization, the electronic control device can be accommodated in the housing of the resolver body. Due to the above characteristics, the ease of use of the resolver is greatly improved, and the effects of the present invention are immeasurable in the market spread of modulated wave resolvers.

It is the figure which showed the modulation wave resolver apparatus. It is the figure which showed the modulation wave generation from a PWM signal. It is a figure showing an example of a band pass filter BPF characteristic. It is the figure which showed an example of the modulated wave waveform. It is the figure which showed the circuit example which detects rotation phase (theta).

The modulated wave resolver device of the present invention is promising for use in AI robots and the like in growing markets, in addition to selling as a single unit, taking advantage of the characteristics that can be miniaturized, by incorporating it into a servo motor. Development can be expected for various applications.
Hereinafter, embodiments of the present invention will be described with reference to FIGS.

FIG. 1 shows an embodiment of a modulated wave resolver device.
Usually, a DSP or FPGA is used for the controller 1. In the case of DSP, a type in which high-speed, high-precision PWM without distortion is incorporated in the peripheral port is used. The controller 1 outputs two-phase PWM signals of orthogonal SIN and COS.

The power switch 2 and the power switch 5 amplify the current of the PWM signal, and a required modulated wave is generated through the bandpass filters BPF3 and BPF6. With this signal, the input coils 4 and 7 of the resolver mechanism 13 are directly driven without a buffer. Since no buffer is required, the space cost is reduced accordingly.
From the resolver mechanical mechanism 13, a modulated wave displaced by a phase angle θ corresponding to the rotation angle is output through the output coil 8. The rotation phase θ is input to the controller 1 through the detection circuit 10 and the phase detection 11 through the differential amplifier 9, and this rotation phase θ, that is, rotation angle information is output from the communication port of the controller 1 to the user interface.

The principle of generating a modulated wave from a PWM signal that is the backbone of the present invention will be described.
The means for obtaining one SIN wave (sine wave) from one PWM square wave is an extension of the following digital signal processing principle.
An expression obtained by expanding a square wave f (t) having a period T into a Fourier series is shown in Expression (1).

It can be expressed as the sum of the sine wave of the fundamental frequency f0 and its odd harmonic component.
From this, it is possible to generate only the sine wave of the fundamental wave by applying the harmonic component appearing at an odd multiple of the fundamental frequency after the third order to the high-order filter and attenuating it.
Figure 2 shows how a SIN wave (modulated wave) is obtained from a PWM rectangular wave. A phase delay due to a filter occurs in the SIN wave with respect to the PWM rectangular wave.

In the modulated wave PWM, the pulse width tp of this rectangular wave is changed within one cycle of the pulse to change the amplitude of the output sine wave.
The PWM pulse width with the maximum output amplitude is when the duty ratio is 50%.
Even if the PWM pulse width exceeds 50% duty ratio, the output amplitude turns to decrease.

The conditions of the high-order filter for attenuating odd terms after the third order in the equation (1) are set as shown in claim 3, and an example thereof is shown in FIG.
The filter characteristics of BPF 3 and 6 that output the modulated wave are that the cutoff frequency of the high-pass low-pass filter starts from the starting point of the frequency higher than the modulated wave basic clock frequency fh (about 500 kHz), and the attenuation at 3 fh is about -60 dB. Set as follows. By strictly observing this characteristic, one modulated wave is generated within the period of the modulated wave basic clock. Furthermore, the amplitude of the modulated wave corresponding to the PWM pulse width can be generated.

In addition, the low-pass high-pass filter is set so as to have a band-pass filter characteristic that starts from a starting point of a frequency whose cutoff frequency is lower than fh and whose attenuation at the signal wave frequency fs reaches about -60 dB.
With this characteristic, it is possible to attenuate the low-frequency swell of the modulated wave due to the frequency component of the signal wave (about 8 kHz) built in the PWM signal.
FIG. 4 shows an example of a modulated wave generated by the PWM signal and BPF.

The controller 1 outputs two-phase PWM signals of SIN and COS that are orthogonal to each other in synchronization with the modulated wave basic clock.
The pulse width of the PWM signal is output in an amplitude modulation arrangement such that the modulation wave output amplitude waveform of the BPFs 3 and 6 outputs SIN and COS modulation waves in synchronization with the signal wave period.
In addition, by incorporating the polarity inversion described in claim 1 of Japanese Patent No. 3047231 into the PWM signal array in the modulated wave, it is possible to restore the 360 ° SIN wave and the COS wave at the time of demodulation.

The modulated wave phase-rotated by the rotation angle θ output from the resolver mechanical mechanism 13 is amplified in amplitude through the differential amplifier 9, and the phase-synchronized detection 10 is performed with the modulated wave basic clock to obtain the envelope of the signal wave.
Next, a signal wave is obtained through a low-pass filter, this signal wave is zero-crossed, phase detection 11 is performed, and the rotation angle of the resolver can be obtained by inputting it to the controller 1.
FIG. 5 shows an example of a series of sequence circuits for detecting the rotational phase θ.

The controller 1 incorporates digital filter processing for attenuating the rotational vibration of the resolver mechanical mechanism 13 itself that is superimposed on the rotational phase θ input to the controller 1 or the electrical modulation wave vibration. By this processing, the input signal is smoothed, and a more stable and highly accurate rotation angle can be detected. A comb filter is a typical digital filter used for such a purpose.
In many cases, the resolver is required to have higher positional accuracy as the speed becomes lower. When the speed is low, the controller's margin processing time increases, and the number of times of arithmetic processing such as a digital filter can be increased, so that higher accuracy can be realized.

  The smoothed rotation phase θ is output to the user interface 12 from the communication port of the controller 1 as resolver rotation angle information. As communication ports, serial communication ports such as general-purpose SPI, I2C, and UART are generally used.

  Since the PWM method of the present invention can realize the small size, light weight, environmental resistance, long life, and low cost of the modulated wave resolver device, the modulated wave resolver device is an AI-equipped robot, information warehouse, machine tool. It can be employed as a key component such as and as an important component. In addition, it is promising as a general-purpose rotation sensor for the ICT revolution as an IoT rotation sensor, and an enormous growth market can be expected in the future.

DESCRIPTION OF SYMBOLS 1 Controller 2 Power switch 3 BPF: SIN band pass filter 4 SIN drive coil 5 Power switch 6 BPF: COS band pass filter 7 COS drive coil 8 Modulated wave output coil 9 Differential amplifier 10 Detection circuit 11 Phase detection 12 User Interface 13 Resolver mechanism

Claims (4)

A controller that outputs a first pulse width modulation signal and a second pulse width modulation signal that are synchronized with the modulation fundamental clock frequency and orthogonal to each other;
A first band-pass filter and a second band-pass filter for generating required amplitude-modulated wave signals from the first pulse width modulation signal and the second pulse width modulation signal, respectively;
First and second input coils driven by the amplitude modulated wave signal generated by the first and second bandpass filters, and an output for outputting a modulated wave displaced by a rotational phase corresponding to a rotation angle A resolver mechanical mechanism including a coil,
The first pulse width modulation signal and the second pulse width modulation signal each include a pulse arrangement having a different pulse width for each pulse and having a frequency smaller than the modulation wave basic clock frequency,
The envelope of the amplitude-modulated wave signal is composed of SIN wave and COS wave signal waves having the frequency of the pulse arrangement,
The first and second band pass filters have a band pass characteristic obtained by synthesizing a high pass low pass filter and a low pass high pass filter ,
The cutoff frequency of the high- pass low-pass filter is a frequency higher than the modulated wave basic clock frequency,
The cut-off frequency of the low- pass high-pass filter is a frequency lower than the modulation wave basic clock frequency,
The high-pass low-pass filter of the first and second bandpass filters has an attenuation amount of a third harmonic of the modulation wave basic clock frequency that is greater than or equal to a predetermined amount, and the low-pass high-pass filter the attenuation at the frequency of the signal wave, have a predetermined or more amount of attenuation, modulation wave resolver apparatus characterized by attenuating the low-frequency swell of the amplitude-modulated wave signal by the signal wave frequency component .   The modulated wave resolver device according to claim 1, wherein polarity inversion is incorporated in the modulated wave signal. The attenuation amount of the third harmonic of the modulated wave basic clock frequency of the first and second bandpass filters is -60 dB or more;
3. The modulated wave resolver device according to claim 1, wherein an attenuation amount at a frequency of the signal wave is at least −60 dB or more. A differential amplifier connected to the output coil of the resolver mechanical mechanism, a detection circuit and a phase detection;
The modulated wave phase-rotated by the rotation angle output from the resolver mechanical mechanism is input to the detection circuit through the differential amplifier, and phase-locked detection is performed with the modulated wave basic clock,
The rotation angle is obtained from the rotation phase by converting the detected modulated wave into the signal wave through a low-pass filter and detecting the phase of the signal wave. The modulated wave resolver device described.